Graduate faculty in six fields of study (chemistry, computer science, education, English, engineering, and psychology) were asked to judge: (a) the importance for academic success of a wide variety of analytical skills; (b) the seriousness of various reasoning errors; (c) the degree to which a variety of "critical incidents" had affected their estimations of students' analytical abilities. Several relatively interpretable dimensions were found to underlie particular clusters of reasoning skills. These dimensions or factors involved (a) the analysis and evaluation of arguments, (b) the drawing of inferences and the development of conclusions, (c) the definition and analysis of problems, (d) the ability to reason inductively, and (e) the generating of alternative explanations or hypotheses. These dimensions were judged to be differentially important for success in the six disciplines included in the study. The authors discuss the study's implications for developing future editions of the GRE analytical ability measure.